The present invention relates to technology for farming benthic organisms such as bivalves, and particularly relates to an apparatus used for farming benthic organisms living in an environment exposed either saltwater or freshwater tides such as venerupis philippinarum, meretrix lusoria, and corbiculidae, to a farming method and to a biofilter using the same.
Bivalves, of which venerupis philippinarum, meretrix lusoria, corbiculidae and the like are representative, are typical popular Japanese seafoods, and are sources of marine protein that can be inexpensively consumed by the general public. Today, however, loss of sand beaches, tidal flats, and the like, due to pollution of ocean waters and rivers, coastal bank reinforcement and the like, has resulted in sharp declines in reserves and catches. Currently, in order to preserve reserves and catches of bivalves, farming is underway in various regions, and in many of the farming methods, spats are artificially seeded on the sea coast and the like and then cultivated in natural environments. However, these conventional farming methods are influenced by changes in the surrounding environment, have high production costs, and cannot provide the market with a stable supply.
Meanwhile, the activities of benthic organisms such as bivalves have an impact on the environment, as they feed by filtering minute phytoplankton that floats suspended in the water and detritus, which is broken pieces of the same, with their gills. In terms of the filtration capacity thereof, venerupis philippinarum, which has a shell length of approximately 3 cm, filters approximately 3 liters of seawater per day, and thus contributes to purification of the ocean waters, from which materials contributing to eutrophication are removed.
Conventional shellfish farming can be divided into mariculture and land-based farming. In terms of farming apparatus in the ocean, spats are cultivated by surrounding a plate or the like, to which spats are attached, with a net and lowering this into seawater, which has the advantage of easily providing an environment that is comparatively close to natural habitat conditions (see JP-3913669-B and JP-3979746-B). However, because the selling price for bivalves is low and production costs are an issue, bivalves remain in a low position in terms of farmed seafood. In particular, costs are presently a problem in terms of achieving land-based farming, and thus this has seen almost no implementation.
For example, in JP-3493357-B, farming facilities for abalone on land are described. In these farming facilities for abalone, an abalone breeding tank is arranged in multiple levels, and the abalone breeding tank is provided with a water supply pipe that supplies seawater and an overflow pipe, while an air supply pipe and a feed supply area are also provided in the breeding tank. Furthermore, in addition to causing seawater to flow into the water supply pipe with a pump, by lowering the overflow pipe, the seawater flows to the lower level water tank, so as to promote the flow of seawater. Furthermore, air is sucked into the air supply pipe with a blower, and compressed air is sprayed out in a froth. Thus, dissolved oxygen is supplied.